1. Field of the Invention
The present invention relates to a semiconductor device including a circuit constructed by thin film transistors (hereinafter referred to as TFTs) and a method of fabricating the same. For example, the present invention relates to an electro-optical device typified by a liquid crystal display panel, and an electronic equipment including such an electro-optical device as a part.
Incidentally, in the present specification, the term xe2x80x9csemiconductor devicexe2x80x9d indicates any devices capable of functioning by using semiconductor characteristics, and any of the electro-optical device, semiconductor circuit, and electronic equipment is a semiconductor device.
2. Description of the Related Art
In recent years, attention has been paid to a technique for constructing a thin film transistor (TFT) using a semiconductor thin film (its thickness is about several to several hundred nm) formed on a substrate having an insulating surface. The thin film transistor is widely applied to an electronic device, such as an IC or an electro-optical device, and especially as a switching element of an image display device, its development has been hastened.
As a typical example of the electro-optical device, a liquid crystal display device, an EL display device, or a contact type image sensor can be cited.
In general, the liquid crystal display device includes a pair of substrates which are opposed to each other at a certain substrate interval, particulate spacers for keeping the certain substrate interval, and a liquid crystal material sealed between the substrates.
The substrate interval of the liquid crystal display device is normally set to 1 to 20 km, and this must be uniformly controlled with accuracy of about xc2x10.1 xcexcm. This is because if fluctuation occurs in the substrate interval, not only deterioration in display quality, such as generation of irregular color or interference fringe, is caused, but also trouble, such as circuit damage or disabled display, is caused by contact of electrodes when the substrate interval is narrowed by an external force. Like this, the spacer is an important member for maintaining the performance of the liquid crystal display element.
Hereinafter, a conventional method of fabricating a liquid crystal display device (TFT-LCD) will be described in brief.
First, a pair of substrates are prepared. TFT elements and pixel electrodes are o formed in matrix form on one of the substrates. Electrodes, color filters or the like are formed on the other substrate. Next, after an alignment film is formed on each of the pair of substrates, a rubbing processing is performed.
Next, particulate spacers are uniformly sprayed on the alignment film of either one of the substrates. Next, the one substrate is combined with the other substrate, and their peripheral portions are sealed with an adhesive for sealing, so that a liquid crystal cell is formed. Next, after the liquid crystal cell is filled with a liquid crystal material by a vacuum injection method, an injection port is sealed.
The foregoing flow of steps is a general fabricating process of a TFT-LCD.
In the above conventional steps, it is difficult to uniformly spray the particulate spacers, and there have been problems that transmissivity is lowered by aggregation of the spacers, and an element just under the spacer is destroyed to generate a leak or short circuit.
Besides, in the step of injecting the liquid crystal material by the vacuum injection method, center portions of the substrates become recess-shaped at both surfaces by pressurization at the time of injection, and in this periphery, the conventional particulate spacer does not have sufficient compression strength and is destroyed, or the spacer is moved and the trace of the movement causes orientation defects.
In the case where the generally used conventional particulate spacers (glass beads, plastic beads, etc.) are used, there is adopted a method of spraying the particulate spacers onto one of substrates. Thus, the spacers are disposed on a pixel electrode, and block incident light or disturb the orientation of liquid crystal molecules. As a result, it has been difficult to adjust the transmitted light amount or coloring. Besides, the particulate spacers are easily charged with static electricity, so that the spacers become easily aggregate and are difficult to be uniformly distributed.
An object of the present invention is to provide a high quality liquid crystal panel having a thickness with high accuracy, which is designed, without using particulate spacers, within a free range in accordance with characteristics of a used liquid crystal and a driving method, and is also to provide a method of fabricating the same.
According to an aspect of the present invention, a semiconductor device includes a first substrate, a second substrate, and a plurality of columnar spacers disposed between the first substrate and the second substrate and maintaining an interval between the first substrate and the second substrate.
Besides, according to another aspect of the present invention, a semiconductor device includes a first substrate, a second substrate, and a plurality of columnar spacers disposed between the first substrate and the second substrate, wherein a radius R of curvature of each of the columnar spacers is 2 xcexcm or less, preferably 1 xcexcm or less.
Besides, in the foregoing respective structures, a height H of each of the columnar spacers is 0.5 xcexcm to 10 xcexcm, preferably 1.2 xcexcm to 5 xcexcm.
Besides, in the foregoing respective structures, a width L1 of each of the columnar spacers is 20 xcexcm or less, preferably 7 xcexcm or less.
Besides, in the foregoing respective structures, an angle a between a tangent plane at a center of a side of each of the columnar spacers and a substrate surface is 65xc2x0 to 150xc2x0.
Besides, in the foregoing respective structures, each of the columnar spacers includes a flat surface at its top portion.
Besides, in the foregoing respective structures, a sectional shape of each of the columnar spacers in a radial direction is a circle, an ellipse, a triangle, a quadrilateral, or a polygon having sides more than the former.
Besides, in the foregoing respective structures, each of the columnar spacers is made of an insulating material.
Besides, in the foregoing respective structures, each of the columnar spacers is formed over a contact portion where a TFT and a pixel electrode are connected to each other.
Besides, the columnar spacers may be formed only at a sealing region, or may be formed at a sealing region and a region of a driver circuit where an element does not exist. Besides, the columnar spacers may be formed at the sealing region and a pixel portion, or may be formed at a region of the driver circuit where an element does not exist and the pixel portion. Besides, the columnar spacers may be formed at the sealing region and a region between the driver circuit and the pixel portion, or the columnar spacers may be formed at a region between the driver circuit and the pixel portion, and the pixel portion.
Besides, the columnar spacers may be formed at a sealing region, over a region of a driver circuit where an element does not exist, and at a pixel portion, or the columnar spacers may be formed over a region of the driver circuit where an element does not exist and at a region between the driver circuit and the pixel portion. Besides, the columnar spacers may be formed at the sealing region, over a region of the driver circuit where an element does not exist, at a region between the driver circuit and the pixel portion, and the pixel portion, or the columnar spacers may be formed at a region between the sealing region and the pixel portion. Besides, the columnar spacers may be formed at a region between the sealing region and the driver circuit, or the columnar spacers may be formed at a region between the sealing region and an end portion of the substrate. Besides, the columnar spacers may be formed at all regions of the substrate.
Besides, in the foregoing respective structures, in the case where the columnar spacers are formed to be in contact with an alignment film, a pretilt angle of liquid crystal is 4xc2x0 to 5xc2x0.
Besides, in the foregoing respective structures, in the case where the columnar spacers are covered with an alignment film, a pretilt angle of liquid crystal is 6xc2x0 to 10xc2x0.
Besides, according to another aspect of the present invention, a semiconductor device includes a display device equipped with a first substrate, a second substrate, and a plurality of columnar spacers disposed between the first substrate and the second substrate, and a touch panel equipped with an optical detecting element.
Besides, according to another aspect of the present invention, a semiconductor device includes a display device equipped with a first substrate, a second substrate, and a plurality of columnar spacers disposed between the first substrate and the second substrate, and a touch panel equipped with a pressure sensitive type detecting element.
Besides, according to another aspect of the present invention, a semiconductor device includes a display device equipped with a first substrate, a second substrate, and a plurality of columnar spacers disposed between the first substrate and the second substrate, and a touch panel equipped with a capacitive type detecting element.
Besides, according to another aspect of the present invention, a method of fabricating a semiconductor device comprises a first step of forming a TFT on a substrate, a second step of forming a flattening film to cover the TFT, a third step of forming an opening in the flattening film to reach to the TFT and forming a pixel electrode, a fourth step of forming an alignment film on the pixel electrode, a fifth step of performing a rubbing processing on the alignment film, and a sixth step of forming a columnar spacer made of an insulating film over a contact portion where the TFT is connected to the pixel electrode.
Besides, according to another aspect of the present invention, a method of fabricating a semiconductor device comprises a first step of forming a TFT on a substrate, a second step of forming a flattening film to cover the TFT, a third step of forming an opening in the flattening film to reach to the TFT and forming a pixel electrode, a fourth step of forming a columnar spacer made of an insulating film over a contact portion where the TFT is connected to the pixel electrode, a fifth step of forming an alignment film to cover the pixel electrode and the columnar spacer, and a sixth step of performing a rubbing processing on the alignment film.
In the foregoing structure, the step of forming the columnar spacer made of the insulating film includes a step of forming the insulating film and a step of patterning the insulating film so that the columnar spacer is formed.